Recently, an image signal containing contents having various aspect ratios and having various aspect ratios has been broadcast on television and has been recorded in a recording medium for sale or rental. When the user watches and listens these contents with an image display device with various aspect ratios, the image display device is required to display a proper display screen by expanding the display screen of the image signal in the horizontal and vertical directions.
FIG. 10 is a block diagram of an image display device of a first conventional example. FIG. 10 shows an analyzing circuit 1, an image decoding circuit 2, a horizontal expanding circuit 3, a vertical expanding circuit 4, a display 5 and an expansion ratio setting circuit 13. The user sets proper horizontal expansion ratio and vertical expansion ratio in the expansion ratio setting circuit according to contents through an operation panel (not shown). The analyzing circuit 1 picks up only desired data from an input image stream. The image decoding circuit 2 decodes the image data picked up in the analyzing circuit 1 into an image signal. The horizontal expanding circuit 3 expands the image signal in the horizontal direction at the horizontal expansion ratio set by the user. The vertical expanding circuit 4 expands the image signal in the vertical direction at the vertical expansion ratio set by the user. The display 5 displays the image signal expanded at each of the horizontal expansion ratio and the vertical expansion ratio. For example, the user determines setting values of the horizontal expansion ratio and the vertical expansion ratio by trial and error so as to remove black zones produced at top and bottom sides or its left and right sides of the screen due to the difference among the aspect ratios of the display, image signal and contents.
Unexamined Patent Publication No. Hei 5-323944 discloses an image display device of a second conventional example. The image display device of the second conventional example intends to display an undistorted image at a correct pixel aspect ratio when image data having a different pixel aspect ratio from the pixel aspect ratio of the display of the image display device is displayed. Based on information on the pixel aspect ratio added to the image data, the image display device of the second conventional example converts the horizontal and vertical image display size by using the size converting means and displays the converted image. Here, the pixel aspect ratio means a ratio of height to width for each pixel represented by digital instead of a ratio of height to width of the whole screen.
However, it is extremely bothersome for the user to set the aspect ratio of the display screen of the image display device for each contents by trial and error. The user frequently forgets to set the aspect ratio or sets an incorrect aspect ratio, resulting in viewing a screen displayed at an improper aspect ratio.
More recently, various aspect ratios have appeared in each of the display, image signal and contents. For example, the aspect ratios of vertical to horizontal size for display are 1:1.33 (=3:4) and 1:1.77 (9:16), the aspect ratios of vertical to horizontal size for image signal are 1:1.33 (=3:4) and 1:1.77 (9:16), and the aspect ratios of vertical to horizontal size for contents are typically 1:1.33 (=3:4), 1:1.66 (European vista) and 1:2.35 (cinema scope). Depending on combination of these aspect ratios, black zones with various widths appear at the top and bottom sides or the left and right sides of the display screen.
When the aspect ratios of the image data, contents and display are the same, the image reproducing device of the second conventional example displays the image data without generating black zones at the top and bottom sides or the left and right sides of the display screen. When the requirement is not satisfied, however, black zones occur at the top and bottom sides or the left and right sides of the display screen. The image reproducing device of the second conventional example lacks the concept of displaying the screen based on the contents aspect ratio.
An object of the present invention is to provide an image display device and an image display method that generate a proper display screen, with a simple operation or automatically, when a combination of an image signal and contents each having various aspect ratios is displayed on a display with various aspect ratios.
An object of the present invention is to provide an image display device and an image display method that generate a display screen that does not cause distortion due to the difference between the image signal aspect ratio and the display aspect ratio with simple operation or automatically without generating black zones at its top and bottom sides or its left and right sides in most cases when a combination of an image signal and contents each having various aspect ratios is displayed on a display with various aspect ratios.